We have had continued success in synthesizing biologically important peptides based on amino acid or nucleotide sequences determined during the course of our studies. We now find that our present peptide synthesizer represents a growingly serious limitation in the progress and pace of our investigations, as it is slow and labor-intensive. As a result, numerous projects are limited by the small number of peptides which can be synthesized and purified with the present equipment. An automatic peptide synthesizer and a high pressure liquid chromatography (HPLC) for purification would accomodate the increasing and already excessive demand for peptide synthesis. We have selected the Model 430A Peptide Synthesizer from Applied Biosystems because of its advanced chemistry, its ease of operation and the consistently high quality results that other investigators have obtained with this instrument. Particularly important is the ability to operate efficiently in an automated mode without constant operator supervision. Also, because of the excellent coupling efficiencies the final product is relatively homogeneous and, therefore, easier to purify. These features will allow Wistar Institute personnel to concentrate their efforts on using the peptides in their experiments rather than on synthesizing and purifying them.